In the following description and the accompanying claims, the expression “closure device” will be used to generally indicate any element movable between an open position and a closed position, respectively opening and closing an access to an inner compartment of a motor vehicle, therefore including, boot, rear hatches, bonnet lid or other closed compartments, window regulators, sunroofs, in addition to the side doors of a motor vehicle, to which the following description will make explicit reference, purely by way of example.
It is known that electrical latches are provided in motor vehicles, for example for controlling opening and closing of the side doors.
An electrical door latch generally envisages a ratchet that is selectively rotatable with respect to a striker fixed to a door post, in order to latch and unlatch the door. The electrical door latch includes a pawl that selectively engages the ratchet to prevent the ratchet from rotating. The electrical door latch includes an electric motor, which is electrically connected to a main electric power supply of the vehicle (tor example to the 12 V battery of the same vehicle), in order to directly or indirectly drive the pawl, via an electrically-operated actuator.
As it is known, a common problem related to electrical latches is that of controlling, as it is also required by security regulations, opening and closing of the doors even in case of emergency situations, such as in case of an accident or crash involving the vehicle.
In particular, during a vehicle crash or other emergency situation, vehicle doors have to be kept closed independently of handle activations or other user or external interventions, so that the electrical latches should be in a so called “double lock” status, while after the crash it should be possible to open the vehicle doors, so that the electrical latches should be promptly brought back to the unlocked status.
In conventional systems, crash management is performed by the main management unit of the vehicle (also known as “vehicle body computer”), which is configured to detect a crash situation by means of crash sensors, and issues suitable control signals to the electrical latches (in particular to the electric motors thereof), in order to drive a double lock during the crash situation and then to cause the unlocking of the electrical latches after the crash.
However, during the emergency situation, failure of the main power supply of the vehicle, or interruptions or breaking of the electrical connection between the main power supply and/or the main management unit of the vehicle and the electric latches, may occur; also, the same vehicle management unit may be subject to damages during the emergency situation.
In that case, the latch management procedure could fail and therefore a reliable and safe operation of the electrical latch assembly could not be assured.
Possible solutions to this problem may envisage a complex handle design, in order to filter peaks of acceleration (or other sensed quantities), which may be due to inertia or impacts during the crash (a solution known as “inertia catch”, that prevents door from unlatching during high impact loads).
However, this solution usually entails the presence of redundant mechanical mechanisms with higher area occupation and weight and additional costs, and also represents a further constriction for designing of the vehicle doors.
Other solutions, as disclosed for example in US 2004/0124027 A1 and US 2007/0199760 A1 envisage the use of a control unit to manage lock/unlock of electronic lock apparatus for vehicle doors, in particular during a crash situation; the control unit is mounted in the vehicle door and coupled to the electronic lock apparatus. However, these solutions are not easy to realize, and do not cope in any manner with the problem of possible failure of the main power supply of the vehicle during the crash.
Moreover, US 2011/0175376 A1 relates to a solution applied to a glove box compartment in the vehicle, which envisages the use of an electronically controlled magnet to increase the magnetic closure resistance of the compartment and avoid unintentional opening of the same compartment during a collision. However, this solution cannot be applied to vehicle doors and to electronic locks thereof, and, again, does not cope in any manner with the problem of possible failure of the main power supply of the vehicle during the crash. Therefore, among other things, a need is felt in the field for an optimized and reliable crash management for an electric latch in a motor vehicle.